Such screen devices having vertically arranged screen rollers are described, for example, in EP 2 662 522 A2 and EP 0 911 476 A.
Tensioning systems are used in such screen devices to keep the screen tensioned in each position in which this screen is rolled up and/or unrolled, so that this screen goes on to sag as little as possible. In screen devices having a screen which can be rolled up and unrolled on an erected screen roller, it is noticed in practice, however, that the end lath, in the fully unrolled state of the screen, cannot generally connect neatly to the structure against which this screen is intended to be unrollable, since in this position it is no longer arranged parallel to the screen roller.
A solution to this problem is described in DE 40 36 892 A1. The herein described screen device comprises on each lateral side of the screen a separate spring sub-system, having a spring element for keeping the respective tensioning cord under tension. In addition, adjusting means are provided for adjusting the spring force of the spring element.